Conventional elastomeric powertrain mounting systems generally provide propulsion system isolation and control propulsion system motion. One common type of powertrain mount is an elastomeric powertrain mount that can provide constant dynamic properties across a range of frequencies. The level of damping is generally increased or decreased by preselecting an elastomeric material having different properties and/or dimensions. Once constructed, set damping rate characteristics are provided regardless of the actual operating conditions encountered by the mount.
Hydraulic mounts were developed, in part, due to the desirability of providing a mount having a high damping coefficient with a single specified peak frequency for relatively high amplitude inputs and a relatively low damping coefficient for lower amplitude inputs. Mount dynamic stiffness and damping performance are determined by characteristics such as, for example, pumping chamber geometry, chamber wall material, and orifice track properties. Additional improvement in the performance characteristics of hydraulic mounts at selected frequency ranges were achieved by employing electronic control of the dynamic characteristics of the mount. This provided a preprogrammed ability to change the response of the mount to optimize dynamic performance.